Hypoxic-hypercapnic ventilatory interaction at the carotid body of awake goats.

Neurophysiological studies have demonstrated that a positive interaction between hypoxic and hypercapnic stimuli occurs at the carotid body (CB). The present study was designed to confirm that this interaction at the CB was translated into a similar interaction in the ventilatory response. By utilizing an awake goat model in which the CB could be selectively perfused using an extracorporeal circuit we avoided confounding central effects. In six goats the CB was stimulated by progressively decreasing PcbO2 from 160 to 40 Torr at two constant levels of PcbCO2, 36 and 61 Torr. The animals breathed room air with supplemental CO2 to maintain systemic isocapnia. The response to CB hypoxia was significantly greater in CB hypercapnia than in CB normocapnia for minute ventilation, tidal volume, respiratory frequency, and mean inspiratory flow rate. We conclude that the hypercapnic-hypoxic interaction at the CB is reflected in the ventilatory responses of the animal.